Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2015

Schedule of Quarterly Financial Information [Table Text Block]

	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
2015	3/31		6/30		9/30		12/31
Total revenues	$	666,371	$	679,112	$	696,289	$	703,193
Operating income	218,171		246,184		257,501		286,964
Income from continuing operations	190,069		298,504		205,375		213,673
Discontinued operations, net	155		114		81		47
Net income *	190,224		298,618		205,456		213,720
Net income available to Common Shares	178,842		285,587		195,859		202,989
Earnings per share – basic:
Net income available to Common Shares	$	0.49	$	0.79	$	0.54	$	0.56
Weighted average Common Shares outstanding	363,098		363,476		363,579		363,828
Earnings per share – diluted:
Net income available to Common Shares	$	0.49	$	0.78	$	0.53	$	0.55
Weighted average Common Shares outstanding	380,327		380,491		380,663		381,220

	First Quarter		Second Quarter		Third Quarter			Fourth Quarter
2014	3/31		6/30		9/30			12/31
Total revenues	$	633,442	$	652,568	$	664,078		$	664,660
Operating income	199,259		228,310		243,274			250,532
Income from continuing operations	81,680		117,210		231,252			226,959
Discontinued operations, net	1,052		510		(62		)	82
Net income *	82,732		117,720		231,190			227,041
Net income available to Common Shares	78,099		111,654		220,707			216,703
Earnings per share – basic:
Net income available to Common Shares	$	0.22	$	0.31	$	0.61		$	0.60
Weighted average Common Shares outstanding	360,470		360,809		361,409			362,018
Earnings per share – diluted:
Net income available to Common Shares	$	0.22	$	0.31	$	0.61		$	0.59
Weighted average Common Shares outstanding	376,384		377,118		377,954			378,886

* The Company did not have any extraordinary items or cumulative effect of change in accounting principle during the years ended December 31, 2015 and 2014. Therefore, income before extraordinary items and cumulative effect of change in accounting principle is not shown as it was equal to the net income amounts disclosed above.

ERPOP [Member]

Schedule of Quarterly Financial Information [Table Text Block]

	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
2015	3/31		6/30		9/30		12/31
Total revenues	$	666,371	$	679,112	$	696,289	$	703,193
Operating income	218,171		246,184		257,501		286,964
Income from continuing operations	190,069		298,504		205,375		213,673
Discontinued operations, net	155		114		81		47
Net income *	190,224		298,618		205,456		213,720
Net income available to Units	185,901		296,941		203,637		211,039
Earnings per Unit – basic:
Net income available to Units	$	0.49	$	0.79	$	0.54	$	0.56
Weighted average Units outstanding	376,696		377,063		377,147		377,380
Earnings per Unit – diluted:
Net income available to Units	$	0.49	$	0.78	$	0.53	$	0.55
Weighted average Units outstanding	380,327		380,491		380,663		381,220

	First Quarter		Second Quarter		Third Quarter			Fourth Quarter
2014	3/31		6/30		9/30			12/31
Total revenues	$	633,442	$	652,568	$	664,078		$	664,660
Operating income	199,259		228,310		243,274			250,532
Income from continuing operations	81,680		117,210		231,252			226,959
Discontinued operations, net	1,052		510		(62		)	82
Net income *	82,732		117,720		231,190			227,041
Net income available to Units	81,192		116,096		229,445			225,261
Earnings per Unit – basic:
Net income available to Units	$	0.22	$	0.31	$	0.61		$	0.60
Weighted average Units outstanding	374,201		374,551		375,116			375,711
Earnings per Unit – diluted:
Net income available to Units	$	0.22	$	0.31	$	0.61		$	0.59
Weighted average Units outstanding	376,384		377,118		377,954			378,886

* The Operating Partnership did not have any extraordinary items or cumulative effect of change in accounting principle during the years ended December 31, 2015 and 2014. Therefore, income before extraordinary items and cumulative effect of change in accounting principle is not shown as it was equal to the net income amounts disclosed above.